Weinland, U.S. Pat. No. 4,105,540 teaches the use of phosphorus containing compounds as anti-foulants in ethylene cracking furnaces. The Weinland patent describes the use of amine neutralized phosphate and phosphite esters to suppress the formation of coking deposits in ethylene furnaces. It will be noted that U.S. Pat. No. 4,105,540 discloses the use of imidazolines in neutralizing amounts rather than in much lesser quantities of filming imidazolines described and claimed in this specification. However, there is no showing in the patent that these materials have specific anticorrosive properties.
U.S. Pat. No. 4,542,253 (Kaplan et al.) discloses an improved method of reducing the corrosion associated with the use of the antifoulants of the Weinland patent. The improvement uses water soluble amines having partition coefficients greater than 1.0 to neutralize the phosphate and phosphite esters. The examples presented in U.S. Pat. No. 4,542,253 show the improved corrosion protection afforded by the phosphorus compounds neutralized with water soluble amines compared with the same phosphorus compounds neutralized with fatty amines of the Weinland patent.
Experience has now shown that the phosphate and phosphite esters neutralized with water soluble amines when used over prolonged periods of time in ethylene furnaces, while providing antifouling protection, do not provide adequate corrosion protection.